[Pw_forum] electron-phonon calculation problem

[yelena]

Dear all,
I've been having problem with electron-phonon calculation. I keep 
having negative phonon frequency in gamma point, -0.00007, nowhere else, 
(so it is not "real" instability, but some numerical problem) but it 
keeps interfering with my lambda.x calculation and all i get is NAN for 
alpha2F and so on. So is there any trick to avoid it? This is clearly 
numerical issue, because other modes are positive and phonon dispersion 
looks as it should be and there is no any instability. Can I somewhere 
manually change that -, maybe? I've tried to increase tr2_ph (and 
decrease it, also) but it keeps happening just the same. And tried 
larger k and q grid. Still the same.

Best Regards,
PhD Student J.Pesic
Center for Solid State Physics,
Institute of Physics Belgrade, Serbia